The present invention has application to an air pallet generally such as that set forth in U.S. Pat. No. 3,948,344 entitled "LOW COST AIR PALLET MATERIAL HANDLING SYSTEM" issued Apr. 6, 1976, and in particular to an air bearing patient mover such as that set forth in U.S. Pat. No. 4,272,856 entitled "DISPOSABLE AIR-BEARING PATIENT MOVER AND VALVE EMPLOYED THEREIN" issued June 16, 1981, of which I am coinventor. Planar air pallets of such type employ at least one flexible material sheet for partially defining a plenum chamber with said one sheet being perforated as by way of small pin holes over a surface area defined by the imprint of the load, which pin holes face an underlying fixed, generally planar support surface. When the plenum chamber is pressurized by low pressure air, the escape of air under pressure through the minute perforations, which open directly to the interior of the plenum chamber, acts to initially jack the load above the flexible sheet and to create a frictionless air film bearing of relatively small height between the support surface and the bottom of the perforated flexible sheet.
In all air pallets including patient movers, it is necessary to provide controlled pillowing of the flexible film or films which may define partially or completely the plenum chamber and to thus establish, by jacking the load to a predetermined height, the ability of the air pallet to ride over surface projections on the underlying support surface. At the same time, excess pressurization of the plenum chamber may cause ballooning of the thin film flexible sheet or sheets, resulting in tilting and rolling of the load off the top of the air pallet. When the load rests on the air pallet prior to pressurization of the plenum chamber, the load tends to press the perforated flexible sheet or sheets into contact with the floor and prevent the entry of air under pressure into the plenum chamber and the subsequent escape of air through the perforations. Air dispersion means are required either interiorly of the plenum chamber or by way of means exterior of the plenum chamber to ensure pressurization of the plenum chamber. Additionally, to permit selective multiple air flow entry to the plenum chamber, such as at the four corners of the patient mover type of air pallet exemplified by U.S. Pat. No. 4,272,856, openings are required within the sealed wall of the dual flexible sheets defining the plenum chamber, either at the sealed edge interface of dual, upper and lower thin flexible sheets, or otherwise. Valve members have been incorporated at the various inlets such that, automatically by air pressurization of the plenum chamber through one of the inlets, the valve members at the other inlets close off those unused inlets to prevent escape of air.
In U.S. Pat. No. 3,948,344, the valves are constituted by the provision of a flap formed at each air inlet as an extension of one of the thin flexible sheets defining a wall of the plenum chamber, such as the bottom flexible sheet bearing the perforations and creating the air bearing. With that flap being a bent over a portion of the sheet internally of the inlet and projecting inwardly into the plenum chamber, by contacting an overlying or underlying opposed sheet or wall member, it functions to seal off and prevent the escape of air through an air inlet at that point by being held in sealing position by developed internal air pressure.
With respect to the patient mover as exemplified by U.S. Pat. No. 4,272,856, each of the multiple air inlets is comprised of at least one outer tube formed of a thin, flexible film material and an inner tube mounted coaxially within the outer tube and comprised of opposed flexible tongues sealed at the ends remote from the plenum chamber to opposite sides of the outer tube with their inner ends being free of each other and from the outer tube. The tongues constitute strips of material of less flexibility than that of the thin flexible film sheets defining either the bottom or top and bottom of the air pallet plenum chamber. As such, during air entry into the plenum chamber through the inlet, the tongues take the curved configuration of the outer tube and are in contact therewith. After pressurization of the plenum chamber, air tending to escape through the inlet causes the tongues to move away from one of the outer tube walls and to press against each other and against the other of the outer tube walls to thereby close off the inlet means. Where multiple inlets are provided, automatically as a result of pressurization of the plenum chamber through one of the inlets, the other unused inlet or inlets are closed off by movement of the tongues away from the outer tube and into contact with each other.
Where the air pallet takes the form of a patient mover, it is desirable to pressurize the plenum chamber starting at the end of the patient mover where the head of the patient rests such that the patient's head rises first during pressurization of the plenum chamber. Jacking of the patient upwardly as a result of plenum chamber pressurization occurs prior to the creation of the air bearing by air escaping from the perforations of the bottom thin flexible sheet. Preferably the air inlet means can be eliminated from the opposite end of the patient mover type of air pallet. Further, it is necessary to insure that during pressurization of the plenum chamber, air does not escape through the second air inlet at the head end of the patient mover to the opposite side, or from any intersecting position as for instance at the same corner, but perpendicular thereto, from that receiving the wand and being subjected to the initial on rush of air under light pressure.
It is, therefore, a primary object of the present invention to provide an improved air pallet and, particularly for a patient mover use in which there is an integration between dual air inlets and their valves of the air pallet which intersects at the same end or extend from both ends of the air pallet, and in which sealing of unused air inlet is insured prior to pressurization of the plenum chamber.